The investigation into the nerve agent attack saw the closure of areas of Salisbury, as police and specialist investigators identified where the Skripals were poisoned.

The highest concentration of the Novichok was found at the Skripals’ front door.

A multimillion pound operation to decontaminate nine locations in the city is under way. Two places that the Skripals visited – the Mill pub and a Zizzi restaurant – are among the places deemed to be still at risk.